US5553060A - Method for maintaining virtual connections given an at least partial outage of connecting paths - Google Patents

Method for maintaining virtual connections given an at least partial outage of connecting paths Download PDF

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Publication number
US5553060A
US5553060A US08/534,923 US53492395A US5553060A US 5553060 A US5553060 A US 5553060A US 53492395 A US53492395 A US 53492395A US 5553060 A US5553060 A US 5553060A
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Prior art keywords
packet switching
network
equipment
switching network
packet
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Expired - Fee Related
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US08/534,923
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English (en)
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Sebastian Obermanns
Richard Schoonhoven
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Siemens AG
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Siemens AG
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5625—Operations, administration and maintenance [OAM]
    • H04L2012/5627—Fault tolerance and recovery

Definitions

  • the present invention relates to a method for maintaining virtual connections in packet switching networks and more particularly, this invention relates to maintaining virtual connections in packet switching networks when there is partial interruption of the connecting paths.
  • the address information contained in the address field of the call request indicates the appropriate network interface location for reconnection with the first packet switching network.
  • a connecting path is defined in the second packet switching network to the appropriate network interface location for connection with the first packet switching network and the call request is forwarded to that location.
  • the address information contained in the address field and address expansion field are exchanged with one another based on the information flag set in the call request.
  • the virtual connection to the switching equipment connected to the called subscriber equipment is set up based on the address information which is now contained in the address field of the call request. This address information identifies the called subscriber equipment.
  • the method requires that the second packet switching network be compatible with and support the "address expansion" protocol. Every packet switching network, however, cannot be assumed to be compatible with this feature.
  • a virtual connection is first completely set up in the second packet switching network upon initiation of the signaling procedure employed by this packet switching network. Only an existing connection and the signaling packets are required to reestablish a virtual sub-connection between the switching equipment of the first packet switching network which is connected to the network interface locations. All packets can be transparently transmitted via the alternate route. Thus, there are no specific requirements whatsoever for the signaling protocol within the second packet switching network. Any arbitrary signaling procedure can be utilized in this packet switching network.
  • FIG. 1 illustrates a block diagram of a communication system which incorporates the present invention.
  • FIG. 1 illustrates a block diagram of a communication system which employs packet switching networks connected to one another via network interfaces in accordance with the present invention.
  • the drawing shows two separate packet switching networks PVN1 and PVN2 which are connected to one another via network interface locations UE1 and UE2.
  • Packet switching network PVN1 is a private packet switching network
  • Packet switching network PVN2 is a public packet switching network.
  • Switching equipment V1 and V2 is located within the packet switching network PVN1.
  • a plurality of respective subscriber equipment is connected to the switching equipment V1 and V2.
  • the switching subscriber equipment is referenced DTE11 through DTE1m or, respectively, DTE21 through DTE2m according to their affiliation with the corresponding switching equipment.
  • a transmission of signaling packets for the purpose of setting up virtual connections between the subscriber equipment and the corresponding switching equipment ensues and the subsequent transmission of data packets given existing virtual connections follows according to CCITT Recommendation X.25.
  • Signaling packets and data packets are also exchanged between the two packet switching networks PVN1 and PVN2 over the two afore-mentioned network interface locations UE1 and UE2, according to this CCITT Recommendation.
  • the switching equipment V1 and V2 which are each capable of carrying out both originating as well as destination switching functions, are in communication with one another via one or more trunk lines.
  • the trunk lines may also be conducted via transit switching centers. Two such transit switching centers are referenced V3 and V4 in FIG. 1.
  • the transmission of signaling packets and data packets ensues according to a trunk protocol based on CCITT Recommendation X.25.
  • the network interface location UE1 is provided in the switching equipment V3 and that the network interface location UE2 is provided in the switching equipment V4.
  • these network interface locations can also be arranged at other transit switching centers or, respectively, at originating and destination switching equipment.
  • An alternate route is selected through the packet switching network PVN2 when a line disturbance occurs with the afore-mentioned virtual connection. This may occur, for example, due to an interruption of one of the trunks provided between the switching equipment V1 and V2. In the example illustrated in FIG. 1, this interruption occurs between the switching equipment V3 and V4.
  • the initial virtual connection is cleared.
  • Switching equipment V3 operates in conjunction with the switching equipment V1 and switching equipment V4 operates in conjunction with switching equipment V2 to accomplish clearing of the connection.
  • the calling subscriber equipment DTE11 connected to the switching equipment V1 and the called subscriber equipment DTE21 connected to the switching equipment V2 are not affected by clearing of the connection.
  • Such a partial clearing of the previously established virtual connection is achieved in accordance with the afore-mentioned trunk protocol on the basis of a specific clear request output by either of the switching equipment V3 or V4.
  • the switching equipment V1 When the clear request is received in the switching equipment V1, it generates a call request that requests the setup of a virtual connection.
  • the address information which identifies the called subscriber equipment (DTE21) which is still retained in the switching equipment V1 is entered into the address field of this call request.
  • This call request is transmitted to the switching equipment V3.
  • the switching equipment V3 recognizes that an alternate route within the packet switching network PVN2 is to be used for the requested call on the basis of the above-assumed line disturbance. In order to select such an alternate route, the call request that has just been received is initially retained, i.e. intermediately stored in the switching equipment V3.
  • the set up of a separate virtual connection within the second packet switching network PVN2 to the network interface location UE2 is then initiated by the switching equipment V3 via the network interface location UE1. This is done in accordance with the signaling procedure defined for the second packet switching network PVN2.
  • a separate call request is first transmitted to switching equipment of the packet switching network PVN2 that is connected to the network interface location UE 1.
  • Address information identifying the network interface location UE2 is contained in the address field of this separate call request.
  • the address information is contained in the data base of the switching equipment V3.
  • a route search for a suitable connecting path to the network interface location UE2 then ensues from the corresponding switching equipment, based on this address information contained in the address field.
  • a virtual connection is set up within this packet switching network between the network interface locations UE1 and UE2, i.e. Between the switching equipment V3 and V4. This virtual connection is set up completely in accordance with the signaling procedure employed by the packet switching network PVN2.
  • the call request initially retained in the switching equipment V3 is then inserted into a data packet as useful information if it is of an appropriate length.
  • This data packet is then transmitted via the packet switching network PVN2 to the switching equipment V4 via the virtual connection which has just been setup. The forwarding of this useful packet thus ensues transparently within the packet switching network PVN2. If the length of a data packet is not sufficient for complete transmission of the call request, the call request is segmented. Individual segments are then transparently transmitted within the packet switching network PVN2 in a plurality of data packets as noted.
  • the switching equipment V4 After depacketing of the received data packet or, respectively, of the received data packets by the switching equipment V4, the latter forwards the call request contained in this data packet or, respectively, in these data packets to the switching equipment V2.
  • the control events required to setup of a virtual connection between the switching equipment V1 and V2 are sequenced within the switching equipment V2.
  • the switching equipment V2 generates a "call accepted" packet which is supplied to the switching equipment V1 via the previously defined alternate route through packet switching network PVN2, i.e. this call accepted signal is also transparently transmitted within the packet switching network PVN2 in one or more data packets.
  • This call accepted signal is also transparently transmitted within the packet switching network PVN2 in one or more data packets.
  • This information is interpreted in the switching equipment V2 in order--after the complete reestablishment of a virtual connection via the packet switching network PVN2--to transmit data packets to the called subscriber equipment DTE21 under that virtual channel number that was also defined for the previously partially interrupted virtual connection.
  • a matching of these momentary counter readings is achieved in the present exemplary embodiment by transmitting information relating to the counter reading of the reception counter kept in the switching equipment V2 to the switching equipment V1 in the afore-mentioned call accepted packet via the alternate route.
  • This information may be located in a user data field of this call accepted packet.
  • the transmission of data packets by the switching equipment V1 is then continued with that data packet whose sequence number corresponds to the counter reading just communicated.
  • the virtual connection which is conducted via an alternate route through packet switching network PVN2 may be continued within the packet switching network PVN1 when an internal connecting path within packet switching network PVN1 becomes available.
  • Information identifying the fact that a virtual connection is conducted via an alternate route is separately retained in the switching equipment which is used by this virtual connection. In the example described above, this information is contained in the switching equipment V3.
  • the above-described virtual connection conducted via the alternate route within the packet switching network PVN2 i.e. Between the switching equipment V1 and V2 in this case, is cleared.
  • a renewed route search is performed based on the address information still stored in the switching equipment V1 for the called subscriber equipment DTE21.
  • a connecting path within the packet switching network PVN1 is subsequently defined to the switching equipment connected to this called subscriber equipment, the switching equipment V2 in this case, and a corresponding call request is transmitted.
  • This call request contains a service signal with which the switching equipment V2 is informed that a virtual connection already conducted via an alternate route is to be reestablished, i.e. that this call request is not to be transmitted to the called subscriber equipment DTE21.
  • the return transmission of a call accepted packet then ensues from the switching equipment V2 in order to again completely reestablish the virtual connection between the subscriber equipment DTE11 and DTE21 that was just partially cleared.
  • the transmission and reception counters kept in the switching equipment V1 and V2 are resynchronized, as already set forth in conjunction with the setup of a virtual connection via an alternate route, in that information regarding the momentary counter reading of the reception counter kept in the switching equipment V2 is again transmitted in the afore-mentioned call accepted packet to the switching equipment V1 and are interpreted in the latter.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)
US08/534,923 1993-06-25 1995-09-28 Method for maintaining virtual connections given an at least partial outage of connecting paths Expired - Fee Related US5553060A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US08/534,923 US5553060A (en) 1993-06-25 1995-09-28 Method for maintaining virtual connections given an at least partial outage of connecting paths

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP93110218A EP0631455A1 (fr) 1993-06-25 1993-06-25 Méthode pour la conservation des connections virtuelles après au moins une disparition partielle de branches de connection
EP93110218 1993-06-25
US26565794A 1994-06-24 1994-06-24
US08/534,923 US5553060A (en) 1993-06-25 1995-09-28 Method for maintaining virtual connections given an at least partial outage of connecting paths

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5828846A (en) * 1995-11-22 1998-10-27 Raptor Systems, Inc. Controlling passage of packets or messages via a virtual connection or flow
US6308281B1 (en) * 1998-09-02 2001-10-23 International Business Machines Corporation Virtual client to gateway connection over multiple physical connections
US7340772B2 (en) 2001-06-13 2008-03-04 Citrix Systems, Inc. Systems and methods for continuing an operation interrupted from a reconnection between a client and server
US7562146B2 (en) 2003-10-10 2009-07-14 Citrix Systems, Inc. Encapsulating protocol for session persistence and reliability
US7661129B2 (en) 2002-02-26 2010-02-09 Citrix Systems, Inc. Secure traversal of network components
US7984157B2 (en) 2002-02-26 2011-07-19 Citrix Systems, Inc. Persistent and reliable session securely traversing network components using an encapsulating protocol

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US4348554A (en) * 1980-03-21 1982-09-07 Bell Telephone Laboratories, Incorporated Method of providing virtual private network telephone service
US4802199A (en) * 1987-06-22 1989-01-31 American Telephone And Telegraph Company Method and apparatus for providing virtual facility communication service
US4884263A (en) * 1986-01-09 1989-11-28 Nec Corporation Packet-switched communications network with parallel virtual circuits for re-routing message packets
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DE4128939A1 (de) * 1991-08-30 1993-03-11 Siemens Ag Verfahren zum aufrechterhalten von virtuellen verbindungen bei einem zumindest teilweisen ausfall von verbindungswegen
US5210740A (en) * 1990-06-21 1993-05-11 Nec Corporation Line switching equipment for switching a personal line to a backup ISDN line
US5307344A (en) * 1991-08-30 1994-04-26 Siemens Aktiengesellschaft Method for setting up virtual connections in packet switching networks

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US4348554A (en) * 1980-03-21 1982-09-07 Bell Telephone Laboratories, Incorporated Method of providing virtual private network telephone service
US4884263A (en) * 1986-01-09 1989-11-28 Nec Corporation Packet-switched communications network with parallel virtual circuits for re-routing message packets
US4802199A (en) * 1987-06-22 1989-01-31 American Telephone And Telegraph Company Method and apparatus for providing virtual facility communication service
US5210740A (en) * 1990-06-21 1993-05-11 Nec Corporation Line switching equipment for switching a personal line to a backup ISDN line
JPH04291595A (ja) * 1991-03-20 1992-10-15 Fujitsu Ltd 仮想私設網接続方式
DE4128939A1 (de) * 1991-08-30 1993-03-11 Siemens Ag Verfahren zum aufrechterhalten von virtuellen verbindungen bei einem zumindest teilweisen ausfall von verbindungswegen
US5307344A (en) * 1991-08-30 1994-04-26 Siemens Aktiengesellschaft Method for setting up virtual connections in packet switching networks
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5828846A (en) * 1995-11-22 1998-10-27 Raptor Systems, Inc. Controlling passage of packets or messages via a virtual connection or flow
US6308281B1 (en) * 1998-09-02 2001-10-23 International Business Machines Corporation Virtual client to gateway connection over multiple physical connections
US7340772B2 (en) 2001-06-13 2008-03-04 Citrix Systems, Inc. Systems and methods for continuing an operation interrupted from a reconnection between a client and server
US7502726B2 (en) 2001-06-13 2009-03-10 Citrix Systems, Inc. Systems and methods for maintaining a session between a client and host service
US8090874B2 (en) 2001-06-13 2012-01-03 Citrix Systems, Inc. Systems and methods for maintaining a client's network connection thru a change in network identifier
US8874791B2 (en) 2001-06-13 2014-10-28 Citrix Systems, Inc. Automatically reconnecting a client across reliable and persistent communication sessions
US7661129B2 (en) 2002-02-26 2010-02-09 Citrix Systems, Inc. Secure traversal of network components
US7984157B2 (en) 2002-02-26 2011-07-19 Citrix Systems, Inc. Persistent and reliable session securely traversing network components using an encapsulating protocol
US7562146B2 (en) 2003-10-10 2009-07-14 Citrix Systems, Inc. Encapsulating protocol for session persistence and reliability

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